The present invention relates to recording media and information recording/reproducing apparatuses, and more particularly, to a recording medium and an information recording/reproducing apparatus permitting optimization of power for recording and/or reproducing information.
The magneto-optical recording medium has attracted much attention as a highly reliable information recording medium which can be rewritten and has a great storage capacity, and has been used in practice as a memory for a computer. As the amount of information to be recorded increases and more compact recording/reproducing apparatuses have been developed, however, there is a need for techniques for recording/reproducing information at even higher density.
Such techniques of recording/reproducing information with higher density include techniques on the recording medium side and techniques on the recording/reproducing apparatus side.
As one of the former techniques, reproducing resolution is improved using a magnetic multi-layer film, in addition to reducing the pitch of recording tracks on the medium. According to the technique of improving reproducing resolution using a magnetic multi-layer film, the magnetic multi-layer film including a recording layer and a reproducing layer is provided within a magneto-optical recording medium. Then, the magnetized state of the recording layer is selectively transferred to the reproducing layer by exchange interaction at the position irradiated with a laser beam for reproduction, taking advantage that the temperature distribution within the laser spot gives a Gaussian distribution maximized in the vicinity of the center of the laser spot, and the magnetized state of the reproducing layer is read out at high density. Such a magneto-optical recording medium which permits high density recording, including the magnetic multi-layer film, is generally referred to as xe2x80x9ca super-resolution magneto-optical recording mediumxe2x80x9d.
Such techniques are mainly grouped into three kinds of techniques at present, that is, FAD (Front Aperture Detection), RAD (Rear Aperture Detection) and CAD (Center Aperture Detection). According to these techniques, a front, rear or central part of a laser spot becomes aperture, so that substantial reproducing region is set smaller than the diameter of the laser spot. As a result, the reproducing density may be increased.
Meanwhile, as one of the latter techniques, a so-called optical super-resolution method is known, according to which a collected light spot exceeding the limit of diffraction of a laser beam is available by inserting a shielding article in the optical path of the laser beam, in addition to reduction of the wavelength of the laser beam. Furthermore, high density recording may be implemented by modulating a magnetic field applied at the time of recording, pulsing a laser beam or the like, and recording at a domain length of 0.15 xcexcm at its shortest is permitted at present.
In a magneto-optical recording medium, information such as the power of a laser beam suitable for recording or reproducing, the rotating speed of a disk or the like is previously stored at the starting end side of the track, and such information is read out during recording or reproducing for use in various kinds of control.
Such data pre-stored for laser beam power is nothing but simple reference, because the shape of the magnetic film varies among media. Therefore, whether the laser power based on the data is optimum for the medium or not should be determined by actually recording or reproducing information to/from the medium using the laser beam. If the track pitch of a recording medium is narrow, and the laser power based on the data is not suitable for the medium in practice, cross erase or cross talk occurs between tracks. Note that the cross erase refers to erroneously erasing a signal recorded at a land or groove when the next groove or land is recorded with a signal.
Furthermore, if the previously recorded data itself is not correct, appropriate recording or reproducing operation to the recording medium cannot be achieved by a recording/reproducing apparatus controlling the power of the laser beam based only on the data.
It is a main object of the present invention to provide a recording medium and an information recording/reproducing apparatus permitting individually determining optimum laser power in practice for the medium on a recording medium-basis.
According to one aspect of the present invention, a recording medium has a recording region for recording information, and one or more calibration regions, each of which has a track shape modulated such that the amplitude of the waveform of a signal reproduced therefrom can change.
According to another aspect of the invention, an information recording/reproducing apparatus for the recording medium as described above includes an optical head for reproducing a signal from the calibration region, and a determination circuit for determining the presence/absence of change in the amplitude of the reproduced signal, thereby determining power for recording and/or reproducing information.
According to yet another aspect of the present invention, the track of a magneto-optical recording medium is divided into a plurality of zones, each of which has a recording region for recording information, and a calibration region having wobbles formed such that the amplitude of the waveform of a reproduced signal can change.
According to yet another aspect of the present invention, a magneto-optical recording medium has a TOC region recorded with a TOC at a part of a track on the starting end side, a calibration region having wobbles such that the amplitude of the waveform of a reproduced signal can change, and a recording region for recording information at another part of the track.
According to a still further aspect of the present invention, a magneto-optical recording medium has a TOC region recorded with a TOC at a part of the outermost periphery of a track on the starting end side, a calibration region having wobbles at a part of the innermost periphery of the track such that the amplitude of the waveform of a reproduced signal can change, and a recording region for recording information at another part of the track.
According to a still further aspect of the present invention, a magneto-optical recording medium has a TOC region recorded with a TOC at a part of the outermost periphery of a track on the starting end side, a calibration region having wobbles at prescribed intervals on the track such that the amplitude of the waveform of a reproduced signal can change, and a recording region for recording information at another part of the track.
According to a still further aspect of the present invention, a magneto-optical recording medium has a TOC region recorded with a TOC at a part of the outermost periphery of a track on the starting end side, a calibration region having wobbles at prescribed intervals along the direction of a segment at a prescribed angle with respect to a segment connecting the center of the magneto-optical recording medium and the starting end of the outermost periphery of the track such that the amplitude of the waveform of a reproduced signal can change, and a recording region for recording information at another part of the track.
According to a still further aspect of the present invention, an information recording/reproducing apparatus for recording/reproducing information to/from a magneto-optical recording medium including a recording region for recording information, and a calibration region having wobbles such that the waveform of a reproduced signal can change includes an optical head for radiating a single laser beam to the magneto-optical recording medium, a determination circuit for determining the waveform of a signal reproduced by the optical head, and a control circuit for controlling the optical head based on the result of determination.
According to an additional aspect of the present invention, an information recording/reproducing apparatus for recording/reproducing information to/from a magneto-optical recording medium including a recording region for recording information, and a calibration region having wobbles such that the amplitude of the waveform of a reproduced signal can change includes an optical head for selectively radiating a single laser beam or a beam formed of a main beam and two side beams to the magneto-optical recording medium, a determination circuit for determining the waveform of a signal reproduced by the optical head, and a control circuit for controlling the optical head based on the result of determination.
According to an additional aspect of the present invention, a magneto-optical recording medium includes a magnetic layer which permits a magnetically recorded signal to be transferred and reproduced, and an information recording/reproducing apparatus includes means for expanding the magnetic domain of the reproduced signal.
According to an additional aspect of the present invention, an optical head is controlled at the time of recording such that a signal is recorded by a main beam in a calibration region, and a signal recorded is reproduced by side beams.
According to an additional aspect of the present invention, a control circuit controls the optical head to radiate a single laser beam to a calibration region at the time of reproducing.
According to an additional aspect of the present invention, an information recording/reproducing apparatus for recording/reproducing information to/from a magneto-optical recording medium including a recording region for recording information, and a calibration region having wobbles such that the amplitude of the waveform of a reproduced signal can change includes an optical head for selectively radiating a single laser beam or a beam formed of a main beam and first to eighth side beams to the magneto-optical recording medium, a determination circuit for determining the waveform of a signal reproduced by the optical head, and a control circuit for controlling the optical head based on the result of determination.
In the recording medium and information recording/reproducing apparatus according to the present invention, change in the amplitude of the waveform of a signal reproduced from the calibration region is evaluated to determine optimum power for recording and/or reproducing.